Timur the Conqueror
From Samarkand, the Turco-Mongol warlord Timur — known in the West as Tamerlane — carved out the last great steppe empire through campaigns that left towers of skulls outside the cities that defied him, while making his capital a jewel of art and architecture. His empire fractured after his death, but his defeat of the Ottoman sultan bought Christian Europe several decades of reprieve.
A weapon or tactic upends the prevailing balance of power and renders an old defensive or offensive order obsolete.